// SPDX-License-Identifier: GPL-2.0
/*
 * drivers/power/process.c - Functions for starting/stopping processes on
 *                           suspend transitions.
 *
 * Originally from swsusp.
 */

#undef DEBUG

#include <linux/interrupt.h>
#include <linux/oom.h>
#include <linux/suspend.h>
#include <linux/module.h>
#include <linux/sched/debug.h>
#include <linux/sched/task.h>
#include <linux/syscalls.h>
#include <linux/freezer.h>
#include <linux/delay.h>
#include <linux/workqueue.h>
#include <linux/kmod.h>
#include <trace/events/power.h>
#include <linux/cpuset.h>

#define PROCESS_TWO 2
#define PROCESS_EIGHT 8
#define PROCESS_TWENTY 20
#define PROCESS_ONETHOUSAND 1000

/*
 * Timeout for stopping processes
 */
unsigned int __read_mostly freeze_timeout_msecs = PROCESS_TWENTY * MSEC_PER_SEC;

static int try_to_freeze_tasks(bool user_only)
{
    struct task_struct *g, *p;
    unsigned long end_time;
    unsigned int todo;
    bool wq_busy = false;
    ktime_t start, end, elapsed;
    unsigned int elapsed_msecs;
    bool wakeup = false;
    int sleep_usecs = USEC_PER_MSEC;

    start = ktime_get_boottime();

    end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);

    if (!user_only) {
        freeze_workqueues_begin();
    }

    while (true) {
        todo = 0;
        read_lock(&tasklist_lock);
        for_each_process_thread(g, p)
        {
            if (p == current || !freeze_task(p)) {
                continue;
            }

            if (!freezer_should_skip(p)) {
                todo++;
            }
        }
        read_unlock(&tasklist_lock);

        if (!user_only) {
            wq_busy = freeze_workqueues_busy();
            todo += wq_busy;
        }

        if (!todo || time_after(jiffies, end_time)) {
            break;
        }

        if (pm_wakeup_pending()) {
            wakeup = true;
            break;
        }

        /*
         * We need to retry, but first give the freezing tasks some
         * time to enter the refrigerator.  Start with an initial
         * 1 ms sleep followed by exponential backoff until 8 ms.
         */
        usleep_range(sleep_usecs / PROCESS_TWO, sleep_usecs);
        if (sleep_usecs < PROCESS_EIGHT * USEC_PER_MSEC) {
            sleep_usecs *= PROCESS_TWO;
        }
    }

    end = ktime_get_boottime();
    elapsed = ktime_sub(end, start);
    elapsed_msecs = ktime_to_ms(elapsed);

    if (wakeup) {
        pr_cont("\n");
        pr_err("Freezing of tasks aborted after %d.%03d seconds", elapsed_msecs / PROCESS_ONETHOUSAND,
               elapsed_msecs % PROCESS_ONETHOUSAND);
    } else if (todo) {
        pr_cont("\n");
        pr_err("Freezing of tasks failed after %d.%03d seconds"
               " (%d tasks refusing to freeze, wq_busy=%d):\n",
               elapsed_msecs / PROCESS_ONETHOUSAND, elapsed_msecs % PROCESS_ONETHOUSAND, todo - wq_busy, wq_busy);

        if (wq_busy) {
            show_workqueue_state();
        }

        if (pm_debug_messages_on) {
            read_lock(&tasklist_lock);
            for_each_process_thread(g, p)
            {
                if (p != current && !freezer_should_skip(p) && freezing(p) && !frozen(p)) {
                    sched_show_task(p);
                }
            }
            read_unlock(&tasklist_lock);
        }
    } else {
        pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / PROCESS_ONETHOUSAND, elapsed_msecs % PROCESS_ONETHOUSAND);
    }

    return todo ? -EBUSY : 0;
}

/**
 * freeze_processes - Signal user space processes to enter the refrigerator.
 * The current thread will not be frozen.  The same process that calls
 * freeze_processes must later call thaw_processes.
 *
 * On success, returns 0.  On failure, -errno and system is fully thawed.
 */
int freeze_processes(void)
{
    int error;

    error = __usermodehelper_disable(UMH_FREEZING);
    if (error) {
        return error;
    }

    /* Make sure this task doesn't get frozen */
    current->flags |= PF_SUSPEND_TASK;

    if (!pm_freezing) {
        atomic_inc(&system_freezing_cnt);
    }

    pm_wakeup_clear(true);
    pr_info("Freezing user space processes ... ");
    pm_freezing = true;
    error = try_to_freeze_tasks(true);
    if (!error) {
        __usermodehelper_set_disable_depth(UMH_DISABLED);
        pr_cont("done.");
    }
    pr_cont("\n");
    BUG_ON(in_atomic());

    /*
     * Now that the whole userspace is frozen we need to disable
     * the OOM killer to disallow any further interference with
     * killable tasks. There is no guarantee oom victims will
     * ever reach a point they go away we have to wait with a timeout.
     */
    if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs))) {
        error = -EBUSY;
    }

    if (error) {
        thaw_processes();
    }
    return error;
}

/**
 * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
 *
 * On success, returns 0.  On failure, -errno and only the kernel threads are
 * thawed, so as to give a chance to the caller to do additional cleanups
 * (if any) before thawing the userspace tasks. So, it is the responsibility
 * of the caller to thaw the userspace tasks, when the time is right.
 */
int freeze_kernel_threads(void)
{
    int error;

    pr_info("Freezing remaining freezable tasks ... ");

    pm_nosig_freezing = true;
    error = try_to_freeze_tasks(false);
    if (!error) {
        pr_cont("done.");
    }

    pr_cont("\n");
    BUG_ON(in_atomic());

    if (error) {
        thaw_kernel_threads();
    }
    return error;
}

void thaw_processes(void)
{
    struct task_struct *g, *p;
    struct task_struct *curr = current;

    trace_suspend_resume(TPS("thaw_processes"), 0, true);
    if (pm_freezing) {
        atomic_dec(&system_freezing_cnt);
    }
    pm_freezing = false;
    pm_nosig_freezing = false;

    oom_killer_enable();

    pr_info("Restarting tasks ... ");

    __usermodehelper_set_disable_depth(UMH_FREEZING);
    thaw_workqueues();

    cpuset_wait_for_hotplug();

    read_lock(&tasklist_lock);
    for_each_process_thread(g, p)
    {
        /* No other threads should have PF_SUSPEND_TASK set */
        WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
        __thaw_task(p);
    }
    read_unlock(&tasklist_lock);

    WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
    curr->flags &= ~PF_SUSPEND_TASK;

    usermodehelper_enable();

    schedule();
    pr_cont("done.\n");
    trace_suspend_resume(TPS("thaw_processes"), 0, false);
}

void thaw_kernel_threads(void)
{
    struct task_struct *g, *p;

    pm_nosig_freezing = false;
    pr_info("Restarting kernel threads ... ");

    thaw_workqueues();

    read_lock(&tasklist_lock);
    for_each_process_thread(g, p)
    {
        if (p->flags & (PF_KTHREAD | PF_WQ_WORKER)) {
            __thaw_task(p);
        }
    }
    read_unlock(&tasklist_lock);

    schedule();
    pr_cont("done.\n");
}
